Density-based separation in multiphase systems provides a simple method to identify sickle cell disease

Abstract

Although effective low-cost interventions exist, child mortality attributable to sickle cell disease (SCD) remains high in low-resource areas due, in large part, to the lack of accessible diagnostic methods. The presence of dense (ρ > 1.120 g/cm 3 ) cells is characteristic of SCD. The fluid, self-assembling step-gradients in density created by aqueous multiphase systems (AMPSs) identifies SCD by detecting dense cells. AMPSs separate different forms of red blood cells by density in a microhematocrit centrifuge and provide a visual means to distinguish individuals with SCD from those with normal hemoglobin or with nondisease, sickle-cell trait in under 12 min. Visual evaluation of a simple two-phase system identified the two main subclasses of SCD [homozygous (Hb SS) and heterozygous (Hb SC)] with a sensitivity of 90% (73-98%) and a specificity of 97% (86-100%). A threephase system identified these two types of SCD with a sensitivity of 91% (78-98%) and a specificity of 88% (74-98%). This system could also distinguish between Hb SS and Hb SC. To the authors' knowledge, this test demonstrates the first separation of cells by density with AMPSs, and the usefulness of AMPSs in point-of-care diagnostic hematology.polymers | erythrocytes | sickle cell anemia | cell sorting | density gradient centrifugation

Tilted Magnetic Levitation Enables Measurement of the Complete Range of Densities of Materials with Low Magnetic Permeability

“…iii) MagLev can be used to perform a range of important, density-based bioanalyses. [13][14][15][16][17] iv) The simplicityof-use, portability, and low cost of MagLev make it particularly attractive for use in resource-limited settings (e.g., schools, mines, archeological sites, field operations, and laboratories in the developing countries).…”

Cellular normoxic biophysical markers of hydroxyurea treatment in sickle cell disease

“…The RI of RBCs is directly related to the concentration of proteins in cytosol, which, in the case of RBCs, is composed mainly of Hb. Accounting for such variations is vital in the case of RBCs of SCD patients, in particular, because they exhibit wider distributions of Hb concentrations (34,35) than healthy patients. In this study, the accuracy of the biophysical measurements has been enhanced by subdividing blood samples from SCD patients into four densities and quantifying densitydependent properties of individual RBCs.…”

From the Bench to the Field in Low‐Cost Diagnostics: Two Case Studies

“…[44,45,47,48] We developed aqueous multiphase systems (AMPS)-mixtures of polymers in water that spontaneously separate into immiscible liquid phases-to separate and visually identify the presence of dense cells characteristic of SCD. [10,12] The densities of the phases of AMPS provide a step-gradient in density. We designed a two-phase system (ρ top = 1.078 g/cm 3 ; ρ bot = 1.129 g/cm 3 ) and a three-phase system (ρ top = 1.077 g/cm 3 ; ρ mid = 1.108 g/cm 3 ; ρ bot =1.120 g/cm 3 ) such that only dense cells characteristic of SCD would be able to sink through the bottom phase (most dense) and form a visible red layer at the interface between the bottom phase and the seal at the bottom of the container.…”

“…[10] The stepgradients that form in AMPS on settling in gravity, or-more rapidly-centrifugation, allowed us to make large batches of these mixtures of polymers and preload them into microhematocrit capillary tubes. The density of red blood cells can change in response to the characteristics of the medium (e.g., pH and osmolality).…”

“…In the last seven years, we have taken two technologies from the bench [7][8][9][10] to the field. [11,12] Each technology, has required a different approach.…”